Switched reluctance motor

ABSTRACT

A stator assembly has coils in a distributed winding configuration. A poly-phase switched reluctance motor assembly may include a stator assembly with multiple coils in a distributed winding configuration. The stator assembly may have a central bore into which a rotor assembly having multiple poles is received and configured to rotate. A method of controlling a switched reluctance motor may include at least three phases wherein during each conduction period a first phase is energized with negative direction current, a second phase is energized with positive current and there is at least one non-energized phase. During each commutation period either the first phase or second phase switches off to a non-energized state and one of the non-energized phases switches on to an energized state with the same direction current as the first or second phase that was switched off. The switched reluctance motor may include a distributed winding configuration.

1 CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/110,780, filed Jul. 11, 2016, which is a national phase entry ofInternational Application No. PCT/US2015/011703, filed Jan. 16, 2015,published in English, and which claims priority from U.S. ProvisionalPatent Application No. 61/928,547, filed on Jan. 17, 2014, thedisclosure of all of which are hereby incorporated herein by reference.

2 STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

3 THE NAMES OF PARTIES TO A JOINT RESEARCH DEVELOPMENT

Not Applicable

4 SEQUENCE LISTING

Not Applicable

5 BACKGROUND OF THE INVENTION 5.1 Field of the Invention

The present technology relates to electronically commutated motors,particularly switched reluctance motors, and the use thereof. Thesetypes of electronically commutated motors produce continuous rotationaltorque without the use of permanent magnets. The present technologyfurther relates to switched reluctance motors having a small size andlow noise output. In some aspects the motors may be used in medicaldevices or apparatus configured to treat, prevent and/or amelioraterespiratory-related disorders.

5.2 Description of the Related Art

5.2.1 Electronically Commutated Motors

One of the subgroups of electronically commutated motors are brushlessD.C. motors. Brushless D.C. motors are well known and used in a range ofdevices. Brushless D.C. motors typically include permanent magnetscoupled to or on a rotor and windings formed on a laminated stator thatform electromagnets when current is applied to the stator. High energypermanent magnets used in motors may be made from materials whichinclude rare earth metals such as samarium-cobalt andneodymium-iron-boron. However, such permanent magnets are expensiveresulting in a higher cost motor. Furthermore the availability of theserare earth metals is limited. To reduce costs other forms of brushlessD.C. motors that do not require permanent magnets or windings associatedwith the rotor were developed.

Another class of electronically commutated motors that do not includepermanent magnets are called switched reluctance (SR) motors. Switchedreluctance motors run by creating reluctance torque, which isproportional to the difference of aligned and non-aligned values of theself-inductance in the SR motor. Conventional SR motors compriseconcentrated windings in the stator that produce torque due to theself-inductance variation slope of one phase and the positive DC currentapplied to that phase. The inductance ratio between the alignedinductance and the unaligned inductance is important in generatingtorque and may vary in the range of 3-8. Consequently SR motors are usedfor the applications where the input power level exceeds several hundredwatts and are generally larger motors with stator outer diametersgreater than 50 mm. Such prior art SR motors have been used to drivedevices such as automotives, vacuum cleaners and washing machines andother large applications. They have not been suitable for driving lowpower (less than a hundred watts) or small (stator outer diameters lessthan 50 mm) high speed devices (up to 60,000 rpm) due to the failure toproduce enough torque in a small arrangement having low inductanceratios. SR motors have also been used in conditions where severeenvironmental conditions occur such as in high or low temperatures.

The stators of SR motors are generally wound with three, four or fivephases in a concentrated winding arrangement. Typically a SR motor hasless rotor poles than stator poles. FIG. 1 shows an example of a threephase SR motor stator and rotor arrangement. The three phases are madeup of three groups of concentrated windings: 10 a, 10 b, 10 c, and 10 dform a first phase; 12 a, 12 b, 12 c and 12 d form a second phase; and14 a, 14 b, 14 c and 14 d form the third phase. In such a concentratedarrangement a coil with sides 10 a and 10 b, is wound around a statortooth or pole 22 of the stator 20, thus the windings are concentratedaround one stator tooth 22. The rotor 30 is formed of a soft magneticmaterial, for example laminated silicon steel, and includes salientmagnetic poles 32 to create a difference in magnetic reluctance betweenrotor and stator along the poles and between the poles.

Generally SR motors have been driven by applying current to energize asingle stator phase at one time and switching the current between statorphases to cause rotation of the rotor. A flux is generated through theenergized stator poles and the rotor poles, which pulls the rotor polestowards and into alignment with the energized stator poles. Switchingthe current to a second adjacent stator phase results in the pulling ofthe rotor poles to align with the second stator phase. The continuousswitching of the current in a sequence to adjacent stator phases aroundthe stator results in rotation of the rotor. Controlling the timing ofthe current switching controls the continuity of the rotor rotation.Switching the current at the optimum position of the rotor is desired toreduce torque ripple or cogging as the rotor rotates. Torque ripple mayresult in vibration and noise within the motor. In attempts to reducetorque ripple the current being applied to adjacent phases during theswitching step has been overlapped. However, when current is applied totwo phases of a conventional SR motor in synchronism the motor is lessefficient, as there is no significant increase in torque despite twicethe power input being provided.

In such SR motors one rotor pole is generally configured to align with asingle stator pole when the rotor is pulled into alignment with theenergized stator pole. For example as seen in FIG. 1, when stator phase10, including stator coil sides 10 a & 10 b and 10 c & 10 d have beenenergized the rotor poles, 32 b and 32 c are pulled to align with statorteeth 1 and 4 respectively. Consequently the normal or radial componentsof the electromagnetic forces are applied to stator teeth and rotorpoles. Such radial forces may be relatively high and can be a source ofvibration and noise within the motor.

Some efforts have been made to reduce the motor noise produced by SRmotors. For example U.S. Pat. No. 5,239,217 describes a multiple phaseSR motor comprising a stator with concentrated windings and multiplerotor poles. Each of the stator poles and the rotor poles may comprisemultiple teeth. The stator includes at least one redundant pole set foreach motor phase to help distribute ovalising forces on the motorassembly as it rotates and reduce motor noise. U.S. Pat. No. 6,028,385suggests reducing the torque ripple effect by using rotor poles having 2wide rotor poles and 2 narrow rotor poles. The three phase reluctancemotor has concentrated windings and includes 12 stator poles with the 4rotor poles. During each energization phase, where one phase isenergized at a time the rotor is sequentially advanced such that theleading edge of a wide rotor pole interacts with a first energizedstator pole and then a narrow rotor pole is drawn into alignment with asecond energized stator pole of the same phase. However, to enablesignificant torque to be produced from such arrangements these SR motorswould be required to be relatively large to maintain an inductance ratioof approximately 7 with the increased number of stator poles.

U.S. Pat. No. 5,111,095 is said to provide a SR motor producingincreased torque and efficiency. The SR motor comprises a stator havingevenly spaced concentrated winding poles and a rotor with unevenlyspaced rotor poles. Two adjacent phases are energized at all times inorder to provide controlled rotation of the rotor. The adjacent windingsare coiled in a direction about the poles of the stator in a manner thatcauses the polarity of the stator poles to have opposite polarities whenthe pair is energized with a current so as to create a magnetic circuitbetween the poles of each pair. The pairs of adjacent stator poles alignwith half (e.g. 4) of the rotor poles and when the next pair of adjacentstator poles are energized these align with the other half (e.g. further4) of the rotor poles. Such a SR motor arrangement would not be suitablefor use in high speed small devices.

Chinese Patent Publication no. CN 102035333A is said to describe apermanent magnet switched reluctance motor adopting a distributedwinding. The stator adopts a three-phase armature winding with adistributed structure, only one winding coil is arranged betweenadjacent stator tooth slot bodies, coils which pass over two statorslots are connected together to form a winding of one phase. A permanentmagnet is also embedded into the stator. The ratio of the number of thestator teeth to the number of the rotor teeth is 6:4, and the number oftheir poles is in the form of 6/4 or 12/8.

There is further need to reduce one or more of the noise, vibrationand/or size of SR motors if they are to be used in medical devicesand/or conditions where low noise is important, such as during sleep.

5.2.2 Motor Applications

Motors are used to drive a variety of devices in a diverse range ofapplications including but not limited to fans, pumps, medical devices,automotive industry, aerospace, toys, power tools, disk drives, andhousehold appliances. Motors have been used in medical devices togenerate a supply of pressurized gas for example in Positive AirwayPressure (PAP) devices and ventilators. These devices generally includepermanent magnet brushless D.C. motors. SR motors generally have notbeen used in such devices due to the generally larger size and higherlevel of noise of SR motors.

The noise produced by some medical devices is required to be relativelylow so as not to disturb the user. In particular for medical devicesthat may be used for long periods of time, such as throughout the day,and/or during sleep, such as PAP devices and/or ventilators the level ofnoise emitted is a significant issue. Sound pressure values of a varietyof objects are listed below:

A-weighted sound Object pressure dB(A) Notes Vacuum cleaner: Nilfisk 68ISO3744 at Walter Broadly Litter Hog: B+ 1 m distance GradeConversational speech 60 1 m distance Average home 50 Quiet library 40Quiet bedroom at night 30 ResMed S9 AutoSet ™ PAP 26.5 device Backgroundin TV studio 20

6 BRIEF SUMMARY OF THE TECHNOLOGY

The present technology is directed towards switched reluctance motorsand devices that comprise such switched reluctance motors.

A first aspect of the present technology relates to switched reluctancemotor comprising a stator having a distributed winding configuration.

Another aspect of the present technology relates to switched reluctancemotor having higher total torque and distributed force.

Another aspect of the present technology relates to switched reluctancemotor having reduced radial forces and noise output.

Another aspect of the present technology relates to a switchedreluctance motor with a stator having an inductance ratio of less than3. For example, technology relates to a switched reluctance motor with astator having an aligned-to-unaligned inductance ratio of less than 3.

One form of the present technology comprises a polyphase switchedreluctance motor assembly comprising a stator assembly including aplurality of coils and a stator with a central bore, and a rotorassembly having a plurality of poles. The rotor assembly is arrangedwithin the central bore of the stator assembly and configured to rotatetherein and the plurality of coils is configured in a distributedwinding configuration.

Furthermore, the stator of the poly-phase switched reluctance motorassembly may include a plurality of projecting stator teeth forming aplurality of stator slots therebetween. Each of the plurality of statorslots may comprise one of the plurality of coils. The total number ofstator slots may be determined as a function of a number of phases and anumber of rotor poles of the motor. The determination of the totalnumber of stator slots may further include a winding distributionparameter.

In some aspects the plurality of coils may include a coil group for eachphase of the poly-phase switched reluctance motor and each of the coilsfor each coil group are uniformly distributed between the stator slots.Each coil group comprises at least one coil.

In some aspects the poly-phase switched reluctance motor assembly mayinclude at least three motor phases and in use two motor phases areenergized at one time during a conduction period. Furthermore one of thetwo energized phases is provided with a positive direction current andthe second of the two energized phases is provided with a negativedirection current. Additionally one of the two energized phases may beswitched off to a non-energized state and one of the non-energizedphases may be switched on to an energized state during each commutationperiod.

Some aspects of the present technology include a poly-phase switchedreluctance motor assembly wherein in use each phase of the motor isenergized with the same current value during at least two consecutiveconduction periods.

One form of the present technology comprises a polyphase switchedreluctance motor assembly including a stator having an outer diameterless than 50 mm.

Another aspect of one form of the present technology is a stator for apoly-phase switched reluctance motor comprising a plurality of statorteeth separated by stator slots and surrounding a central bore and aplurality of coils that are configured in a distributed windingconfiguration. The plurality of coils may include a coil group for eachphase of the poly-phased switched reluctance motor and the coil groupmay include one or more coils. The central bore of the stator assemblyis configured to receive a rotor assembly having a plurality of poles.Furthermore each of the stator slots may comprise one of the pluralityof coils.

Another aspect of one form of the present technology is a stator for apoly-phase switched reluctance motor having an inductance ratio of lessthan 3.

Another aspect of one form of the present technology is a stator for apoly-phase switched reluctance motor having an outer diameter of lessthan 50 mm.

Another aspect of one form of the present technology is a positiveairway pressure device comprising a poly-phase switched reluctance motorincluding a stator having a distributed winding configuration. Thepositive airway pressure device configured to provide a supply ofpressurized breathable gas.

Another aspect of one form of the present technology is a system fortreating a respiratory disorder comprising a therapy device configuredto provide a supply of pressurized breathable gas, the therapy devicecomprising a poly-phase switched reluctance motor including a statorhaving a distributed winding configuration. The system may furtherinclude an air delivery conduit and a patient interface configured toreceive the supply of pressurized gas from the therapy device via theair delivery conduit and deliver the supply of pressurized gas to apatient. The system may additionally include a humidifier configured tohumidify the supply of pressurized gas.

An aspect of one form of the present technology is a method ofcontrolling a switched reluctance motor comprising at least threephases. The method comprising during each conduction period energizing afirst phase with a negative direction current, energizing a second phasewith a positive current and having at least one non-energized phase andduring each commutation period switching off one of the first phase orthe second phase to a non-energized state and switching on one of thenon-energized phases to an energized state with the same directioncurrent as the first or second phase that was switched off. Furthermorethe switched reluctance motor may include a distributed windingconfiguration.

Embodiments of the switched reluctance motor may be implemented withoutthe use of permanent magnets for rotation of the rotor or such as havingno permanent magnets within the stator.

Of course, portions of the aspects may form sub-aspects of the presenttechnology. Also, various ones of the sub-aspects and/or aspects may becombined in various manners and also constitute additional aspects orsub-aspects of the present technology.

Although described in relation to medical devices the SR motors of thepresent technology may be used in a range of applications.

Other features of the technology will be apparent from consideration ofthe information contained in the following detailed description,abstract, drawings and claims.

7 BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present technology is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements including:

7.1 Motor

FIG. 1 shows an example of a prior art switched reluctance motor 6/4stator and rotor configuration with concentrated windings.

FIG. 2A shows an exemplary switched reluctance motor 6/2 stator androtor configuration with distributed windings in accordance with anotheraspect of the present technology.

FIG. 2B shows an exemplary switched reluctance motor 12/4 stator androtor configuration with distributed windings in accordance with oneaspect of the present technology.

FIG. 2C illustrates the winding configuration of the exemplary SR motorshown in FIG. 2B.

FIG. 2D illustrates the self and mutual inductances versus themechanical angle of the rotor of the exemplary SR motor of FIG. 2B.

FIG. 2E illustrates an exemplary pattern of applying current to thedifferent phases of the SR motors of FIG. 2B.

FIG. 2F illustrates the torque produced by the exemplary SR motor inFIG. 2B for different current sequences.

FIG. 2G illustrates exemplary flux paths for a rotor mechanical angle of0°, 180° and 360° as the minimum mutual inductance position when phase Ais provided with positive current and phase C is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2H illustrates exemplary flux paths for a rotor mechanical angle of15° and 195° as the maximum mutual inductance position when phase A isprovided with positive current and phase B is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2I illustrates exemplary flux paths for a rotor mechanical angle of30° and 210° as the minimum mutual inductance position when phase B isprovided with positive current and phase C is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2J illustrates exemplary flux paths for a rotor mechanical angle of45° and 225° as the maximum mutual inductance position when phase A isprovided with positive current and phase C is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2K illustrates exemplary flux paths for a rotor mechanical angle of60° and 240° as the minimum mutual inductance position when phase B isprovided with positive current and phase A is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2L illustrates exemplary flux paths for a rotor mechanical angle of75° and 255° as the maximum mutual inductance position when phase B isprovided with positive current and phase C is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2M illustrates exemplary flux paths for a rotor mechanical angle of90° and 270° as the minimum mutual inductance position when phase C isprovided with positive current and phase A is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2N illustrates exemplary flux paths for a rotor mechanical angle of105° and 285° as the maximum mutual inductance position when phase B isprovided with positive current and phase A is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2O illustrates exemplary flux paths for a rotor mechanical angle of120° and 300° as the minimum mutual inductance position when phase C isprovided with positive current and phase B is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2P illustrates exemplary flux paths for a rotor mechanical angle of135° and 315° as the maximum mutual inductance position when phase C isprovided with positive current and phase A is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2Q illustrates exemplary flux paths for a rotor mechanical angle of150° and 330° as the minimum mutual inductance position when phase A isprovided with positive current and phase B is provided with negativecurrent for the SR motor of FIG. 2B.

FIG. 2R illustrates exemplary flux paths for a rotor mechanical angle of165° and 345° as the maximum mutual inductance position when phase C isprovided with positive current and phase B is provided with negativecurrent for the SR motor of FIG. 2B.

7.2 Motor Assembly

FIG. 3A is a perspective view of an example motor assembly in someimplementations of the present technology.

FIG. 3B is a cross sectional view of the motor assembly of FIG. 3A.

FIGS. 3C and 3D show outside and inside perspective views respectivelyof an end bell housing component of the motor assembly of FIG. 3A.

FIGS. 3E and 3F show outside and inside perspective views respectivelyof a housing of the motor assembly of FIG. 3A.

FIG. 3G is an perspective view of an example rotor assembly for themotor assembly of FIG. 3A.

FIG. 3H is a perspective view of an example stator suitable forimplementation in the motor assembly of FIG. 3A.

FIG. 3I is a schematic plan view of the stator assembly of FIG. 3Hillustrating inclusion of phase coils.

FIG. 3J is a top view illustration of a wound stator.

7.3 System

FIG. 4 shows a system in accordance with the present technology. Apatient 1000 wearing a patient interface 3000, receives a supply of airat positive pressure from a PAP device 4000. Air from the PAP device ishumidified in a humidifier 5000, and passes along an air circuit 4170 tothe patient 1000. A bed partner 1100 may also be present when thepatient uses the system.

7.4 Pap Device

FIG. 5A shows a PAP device in accordance with one form of the presenttechnology.

FIG. 5B shows a schematic diagram of the pneumatic circuit of a PAPdevice in accordance with one form of the present technology. Thedirections of upstream and downstream are indicated.

FIG. 5C shows a schematic diagram of the electrical components of a PAPdevice in accordance with one aspect of the present technology.

FIG. 5D shows a schematic diagram of the algorithms implemented in a PAPdevice in accordance with an aspect of the present technology. In thisfigure, arrows with solid lines indicate an actual flow of information,for example via an electronic signal.

FIG. 5E is a flow chart illustrating a method carried out by the therapyengine module of FIG. 5D in accordance with one form of the presenttechnology.

7.5 Humidifier

FIG. 6A shows a humidifier in accordance with one aspect of the presenttechnology.

FIG. 6B shows a schematic of a humidifier.

8. DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

Before the present technology is described in further detail, it is tobe understood that the technology is not limited to the particularexamples described herein, which may vary. It is also to be understoodthat the terminology used in this disclosure is for the purpose ofdescribing only the particular examples discussed herein, and is notintended to be limiting.

8.1 Switched Reluctance Motor

8.1.1 Stator

In one form, the present technology comprises a switched reluctancemotor including a stator having distributed coil windings. In a case ofa distributed windings configuration, the coils are placed or wound intothe slots. With such a distributed winding, each coil winding mayencircle or encompass at least two stator teeth (or more) while skippingover at least one stator slot (or more). The coils may have full pitchor fractional pitch. The number of slots that are occupied with thecoils of one phase depend on the number of rotor poles and a windingdistribution parameter. The winding distribution parameter indicates howmany adjacent slots are occupied with coil segments of the same phase.

In the exemplary stator assemblies as shown in FIGS. 2A and 2B thewinding distribution parameter is 1 as each coil segment (i.e., the coilportion within a stator slot) for each phase is adjacent a coil segmentfrom another phase and not adjacent another coil segment from the samephase. There may be one or more coils for the same phase and coils fromthe same phase are referred to as a coil group. Each coil groupcomprises at least one coil, such as one, two, three, four, five or morecoils per coil group. Each of the coils in a coil group includes twocoil segments (i.e. a pair of coil segments) provided in differentstator slots.

FIG. 2A shows a stator and rotor configuration for a three phase SRmotor having 6 stator poles (6 stator teeth 120 and 6 stator slots 122)and 2 rotor poles 130 according to an example of the present technology.In FIG. 2A, each phase includes one coil for each phase and the coil iswound with two coil segments within two stator slots 122. The segmentsare connected by the end turns of the winding which is not shown in thefigure. The A phase coil includes A+ and A− coils segments 110 a, 110 brespectively located within stator slots between stator teeth 1 & 6 andstator teeth 3 & 4 respectively. The B phase coil includes B+ and B−coil segments, 112 a, 112 b respectively that are located within statorslots between stator teeth 4 & 5 and stator teeth 1 & 2 respectively.The C phase coil includes C+ and C− coil segments 114 a, 114 brespectively that are located within stator slots between stator teeth 2& 3 and stator teeth 5 & 6. Thus, each stator coil is located in a slotbetween two stator teeth and adjacent winding coils from differentphases share an association with stator teeth that separate them. Inthis configuration, each stator coil segment from the same phase isseparated from the other stator coil segment of the same phase by threestator teeth. The coils are not wound around a single stator tooth.

FIGS. 2B and 2C illustrate a stator and rotor configuration for a threephase SR motor having 12 stator poles (12 stator teeth 220 and 12 statorslots 222) and 4 rotor poles 230 according to another example of thepresent technology. In FIG. 2C the slots are numbered “1” through “12”and each tooth, although not shown with a number, may be considered tohave the same number as the numbered slot to the left of the tooth.(i.e., stator tooth 1 is between stator slots 1 and 2, etc.) In thisarrangement there are two coil winding groups for each phase, each groupincludes one coil formed of two coil segments that occupy two statorslots. The coil segments are distributed evenly around the stator andeach coil segment for a single phase is separated by three stator teeth.In FIG. 2C, stator slots numbered 2 and 12 and coil 214 b are each showntwice simply for purposes of more clearly illustrating the coil windingspattern. For example, phase A coil segments 210 a and 210 b areseparated by stator teeth 1, 2 and 3 are wound through slots numbered 1and 4 to be located in slots 1 and 4. In the illustrated example phase Acoil segments 210 a, 210 b, 210 c and 210 d are located in stator slots1, 4, 7 and 10, between stator teeth 12 and 1; 3 and 4; 6 and 7; and 9and 10 respectively. Phase B coil segments 212 a, 212 b, 212 c and 21 dare located in slots 9, 12, 3 and 6, between stator teeth 8 and 9; 11and 12; 2 and 3; and 5 and 6 respectively. Phase C coil segments 214 a,214 b, 214 c and 214 d are located in slots 11, 2, 5 and 8, betweenstator teeth 10 and 11, 1 and 2; 4 and 5; and 7 and 8 respectively.Thus, each stator slot includes a single coil segment from one coil. Askilled addressee would appreciate that the coils or coil segments forthe different phases may be arranged in a different order.

Although FIGS. 2A and 2B refer to three phase motors (i.e., phases A Band C), it is to be understood that the motor may comprise a differentnumber of phases such as two, four, five or more phases. The number ofstator slots or stator teeth for different SR motor configurations maybe determined as a function of the number of phases and the number ofrotor poles. The winding distribution parameter may also be used in thisdetermination for example using the following equation:Total number of stator slots=number of phases×number of rotorpoles×winding distribution parameter.Thus, the total number of stator slots may be a multiple of number ofphases and number of rotor poles of the motor. Moreover, the totalnumber of stator slots may be a multiple of a winding distributionparameter.

The stator is formed as a lamination stack for example of steellaminations such as silicon steel e.g. M19 grade silicon steel(M19_29G). The rotor may be formed of the same material as the stator oranother type of ferromagnetic material like ferrite or iron cobaltalloys. The coils may be formed of any wire gauge preferably in therange of 26 to 32 gauge wire, for example, each of the coils may beformed from American wire gauge (AWG) 30. The number of turns of thewire is determined by the voltage of the motor. For example the coilsmay include 30-40 turns per coils such as 34 turns per coil. In somecases, each turn of the coil may have one or more wires in hand such asa number in a range of 2 to 10 wires in hand per turn. For example, itmay have six wires in hand per turn. Thus, in one example winding, thewire may be AWG 30, and each coil may have 34 turns with 6 wires inhand. However, a skilled addressee would understand that the coils maybe formed of other material and include a different number of turns percoil and number of wires etc.

A SR motor having a distributed winding configuration distributes theflux between the teeth that each of the phase coils is associated ratherthan concentrating the flux in a single stator tooth. This results inthe radial electromagnetic forces acting between the stator and therotor being distributed along the stator teeth that are associated withthe energized coils. Thus, in the three phase stator arrangementillustrated in FIG. 2B the electromagnetic force is applied to fourteeth with a 90° mechanical phase shift at the same time, see FIGS. 2Gto 2R. In contrast a conventional three phase concentrated stator as inFIG. 1 applies the electromagnetic force to two teeth with a 180° phaseshift at the same time. Therefore in the exemplary SR motor withdistributed windings the peak radial force applied to each tooth is lessthan in a conventional concentrated winding. In other words, thedistribution permits a reduction in radial forces. For example in a SRmotor comprising a 12/4 rotor configuration as illustrated in FIG. 2Bthe peak radial force in each tooth may be 329 Newtons compared to 518Nper tooth in a 6/4 concentrated winding conventional SR motor asillustrated in FIG. 1. The distribution of the radial electromagneticforces reduces vibration and consequently reduces noise produced fromthe SR motor.

The SR motor including a distributed winding configuration of thepresent technology may have a low aligned to unaligned inductance ratio,such as an inductance ratio of less than 3, or less than 2.5 e.g.between 2 and 2.5.

Advantageously the SR motor including a distributed windingconfiguration according to the present technology allows for smallerlower power SR motors to be made that produce enough torque to run smallhigh speed devices (up to 60,000 rpm). A small SR motor is understood tomean a SR motor having a stator outer diameter of less than 50 mm, suchas 48 mm, 47 mm, 46 nm, 45 nm, 44 mm, 43 mm or less. However, it is tobe understood that a SR motor having a distributed winding configurationmay also be used in larger motors than have stator outer diametersgreater than 50 mm.

8.1.2 Rotor

The rotor includes at least two rotor poles 130, 230, the rotor polesform rotor teeth that extend out from a central rotor core. In FIG. 2A,the rotor has two rotor teeth 131-1, 131-2. In FIG. 2B, the rotor hasfour rotor teeth 131-1, 131-2, 131-3, 131-4. Each of the rotor teeth mayhave a width that is wider than the width of a single stator tooth. Thiscan help to distribute the radial electromagnetic forces acting betweenthe stator and the rotor between multiple stator teeth that areassociated with the energized coils. In this example of FIG. 2B, thewidth of a rotor tooth may be approximately equal to the width of astator tooth (e.g., the length of the inner arc surface of an end of thestator tooth) plus some width such as a function of a measure of thewidth of the gap between adjacent stator teeth. The gap 233 being thestator slot width at the inner end of the stator slot (the inner endbeing the end closest to the rotor). For example, the width of a rotortooth may be approximately equal to the width of the stator tooth plus amultiple (e.g., two times) of the width of the gap between stator teeth.In this regard, the rotor width may be understood to refer to a lengthalong a surface at an end of the rotor tooth that may be formed as anarc at an end of each tooth of the rotor.

In some versions of the present technology, each stator tooth may havetooth tips 213 a, 213 b (labeled in FIG. 2B) that form projections oneither side of a stator tooth and that extend the width of the statorwhile still permitting a gap between the stator teeth. The teeth tipscan serve to smooth the field in air gap between stator teeth and helpto reduce noise. The tips may also help with keeping the winding in thegap or helping to prevent the winding from shifting to the rotor area ofthe bore. In some versions of the present technology, a suitable statortooth width may be about 2.4 mm. However, other widths may be employed,such as a width in a range of 1.75 mm to 5 mm. That stator tooth widthmay increase by the width of the tooth tips when included. In somecases, the rotor pole width may be about 7 mm. However, other widths maybe employed, such as a width in a range of 5 mm to 10 mm.

The central angles of the stator and rotor poles may be as significantas absolute width values of the teeth. For example, in some typicalmotor designs, the central angle of the stator and rotor poles may beapproximately the same or have a very small difference between them suchas a few degrees. However, in some versions of the present technology,the angles may be significantly different, such as having an angledifference of more than several degrees (e.g., more than 5 degrees suchas in a difference range from 3 degrees to 40 degrees, or such as in adifference range of 5 degrees to 30 degrees. For example, the statorcentral angle, such as the angle formed from the center of the statorwith imaginary lines extending radially to the edges of a stator's toothor stator's tips (see, e.g., angle SA illustrated in FIG. 2B) may beabout 13 degrees (e.g., 13.12°). In such an example, the rotor centralangle, such as the angle formed from the center of the rotor withimaginary lines extending radially to the edges of a rotor's tooth (see,e.g., angle RA illustrated in FIG. 2B) may be about 40 degrees (e.g.,40.14°). Such a difference between the stator central angle and rotorcentral angle is very significant (e.g., approximately 27 degrees).

The rotor may be formed of a suitable material such as silicon steele.g. M19 grade silicon steel (M19_29G) or another type of ferromagneticmaterial like ferrite or iron cobalt alloys.

8.1.3 Motor Control

As mentioned previously, torque in SR motors is proportional to thedifference in a phase self-inductances in an aligned and non-alignedposition when the appropriate phase is energized. It has been determinedthat using a distributed stator winding configuration in a SR motor ofthe present technology may produce a significant mutual inductancevariation between certain positions of the rotor. This mutual inductancemay be utilized to produce a higher torque at small power (less thanhundred watts such as 90 Watts, 60 Watts or 50 Watts) SR motor design.FIG. 2D illustrates an example of the self and mutual inductancesproduced in a SR motor according to the present technology. Theself-inductances Laa, Lbb and Lcc show significantly less variation inthe inductance generated at the different rotor positions than themutual inductances Lab, Lac and Lbc. The mutual inductance variation isapproximately eight times the variation range generated by theself-inductances in the example shown. As torque is proportional to thedifference of align and non-align values of the inductance in SR motorsthe mutual inductance may be utilised to produce a larger portion of thetorque. The total torque produced in the motor is the sum of thecomponents related to self-inductance and the mutual inductance.

The stator of the SR motor of the present technology includes at leastthree motor phases. Due to the mutual inductance producing a largeportion of the torque, the SR motor of the present technology may beconfigured to energize two phases at the same time during eachconduction period. A first phase may be energized with a positivedirection current and a second phase may be energized with a negativedirection current resulting in a net flux increase in the motor andproducing a higher torque. Two phases are energised at the same time andfollow a specific sequence to cause the rotor to rotate. Each phase ofthe motor may be energized with the same current value during at leasttwo consecutive conduction periods. For example in some configurationsone of the two energized phases is switched off to a non-energized stateand one of the non-energized phases is switched on to an energized stateduring each commutation period. The timing of the commutation period orswitching is controlled to facilitate smooth rotation of the motor andreduce cogging.

FIG. 2E shows an exemplary commutation for a SR motor comprising adistributed stator as shown in FIG. 2B. In a first step phase A may beenergised with a positive direction current, phase B may be energisedwith a negative direction current and phase C may be non-energised (zerocurrent) (i.e., A+B−). This will cause the rotor to move towards thealignment position shown in FIG. 2H. In the second step, phase A maycontinue to be energised with a positive direction current, phase B isswitched off to an non-energized state (zero current) and phase C isenergized with a negative direction current (i.e. A+C−). This will causethe rotor to move towards the alignment positions shown in FIG. 2J. Inthe third step, the phase A is switched off to an non-energized state(zero current), phase B is energized with a positive direction currentand phase C continues to be energized with a negative direction current(i.e. B+C−). This will cause the rotor to move towards the alignmentposition shown in FIG. 2L. This sequential switching of the phasescontinues such that the fourth step would be B+A− causing the rotor tomove towards the alignment position shown in FIG. 2N. The fifth step,C+A−, causing the rotor to move towards the alignment position shown inFIG. 2P. The sixth step, C+B−, causing the rotor to move towards thealignment position shown in FIG. 2R. Then the cycle repeats again byreturning to A+B− to provide a full 360° revolution of the rotor. Thespecific timing of the switching or commutation of the energization ofthe phases may be varied to adjust the performance of the motor andreduce torque ripple.

FIG. 2F shows an example of the torque produced for different currentsequences relative to the rotor position in a SR motor comprising astator and rotor configuration as shown in FIG. 2B. For example for arotor position between 8° to 38°, the slope of Lac produces the largestproportion of the torque.

${T_{a} = {{\frac{1}{2}\frac{\partial L_{aa}}{\partial\theta}i_{a}^{2}} + {\frac{\partial L_{ab}}{\partial\theta}i_{a}i_{b}} + {\frac{\partial L_{ac}}{\partial\theta}i_{a}i_{c}}}},$Where Ta the instantaneous torque value, i_(a), i_(b) and i_(c) areinstantaneous values of the current in phases A, B and C respectively.L_(aa) is the total inductance of phase A. L_(ab) is the mutualinductance between phases A and B and L_(ac) is the mutual inductancebetween phases A and C respectively.

In contrast in a conventional SR motor, where only the self-inductancecomponent is producing the torque,

${i.e.\mspace{14mu} T_{a}} = {\left( {\frac{1}{2}\frac{\partial L_{aa}}{\partial\theta}i_{a}^{2}} \right).}$

A method of controlling a switched reluctance motor comprising at leastthree phases may include during each conduction period energizing afirst phase with a negative direction current, energizing a second phasewith a positive current and having at least one non-energized phase andduring each commutation period switching off one of the first phase orthe second phase to a non-energized state and switching on one of thenon-energized phases to an energized state with the same directioncurrent as the first or second phase that was switched off. The switchedreluctance motor may include a distributed winding configuration asdescribed above.

In some aspects of the present technology the SR motor may be controlledusing a sensorless control. In this arrangement when the rotor passesthe non-energized phase, the back EMF, induced in the phase can bedetected and filtered in order to remove the noise. The signal isproportional to the rotor angle and may be used to estimate the positionof the rotor.

8.1.4 Motor Assembly

An example of a motor assembly 3002 that may be implemented with theswitched reluctance motor technology described herein is illustrated inFIGS. 3A through 3J. As seen in FIGS. 3A and 3B, the motor assembly 3002may include a motor housing 3100, an end bell 3110 and one or moreimpeller(s) 3120. An example end bell is shown in FIGS. 3C and 3D. Anexample motor housing is illustrated in FIGS. 3E and 3F. The motorassembly may also optionally include an encoder 3130, such as an opticalencoder to detect rotation and/or positioning (e.g., absolute orrelative movement) of the shaft of the rotor assembly. As seen in FIG.3B, a housing of the encoder may be coupled to the end bell 3110 withone or more fasteners, such as screws 3132 a. Corresponding fastenerholes 3135 on the end bell 3110 and motor housing 3100 as seen in FIGS.3A, 3C, 3D and 3F receive additional fasteners, such as screws 3132 betc., for joining and holding the end bell 3110 and motor housing 3100together. Other types of fasteners may also be implemented such asbolts, snap fit structures, clips, rivets, etc. for joining thestructures of the motor assembly. As shown in FIG. 3f , the motorhousing may optionally include a wiring aperture 3235. The wiringaperture can permit lead wires of the coils of the stator assembly topass out of the motor assembly when the stator assembly is installedwithin the motor assembly.

As seen in more detail in the cross sectional view of FIG. 3B, the motorhousing 3100 and end bell 3110 may contain the stator assembly 3140 androtor assembly 3150 (on FIG. 3G). (the rotor assembly 3150 is not shownin FIG. 3B). The stator assembly 3140 may include a stator 3141 andcoils in any configuration as previously described such as the statorconfiguration illustrated in FIG. 2B. As illustrated in FIG. 3H, thestator 3141 of such a stator assembly, like the rotor, can be formed ina laminated stack. An example coil configuration is illustrated in FIGS.31 and 3J showing the stator 3141 with stator teeth 220 and stator slots222. Coil groups for phases A, B and C are shown.

The rotor assembly 3150 may include a rotor in any configuration aspreviously described such as the rotor configuration also illustrated inFIG. 2B. In this regard, the rotor assembly may include a rotor 3152 andshaft 3154 as illustrated in FIG. 3G. As illustrated, the rotor may be alaminated rotor stack (e.g., a plurality of stacked plates) that arebonded to the shaft using a primer and adhesive. The rotor assembly maybe mounted for rotation within the motor housing 3100 and end bell 3110with a set of bearings 3160 a, 3160 b through which the shaft ends areinserted. The bearings 3160 a, 3160 b may each reside in a cylindricalbearing seat 3161 a, 3161 b in each of the end bell 3110 and the motorhousing 3100 respectively. The shaft may also be positioned within theassembly with a spring 3162. The impeller(s) 3120 may be press fit at animpeller end of the shaft 3154 opposite an encoder end of the shaft3154. Alternatively, the shaft may have impellers at both ends of theshaft (not shown). The rotor assembly may also include one or morebalance rings 3164 a, 3164 b. The motor assembly or the impeller(s) maybe inserted or positioned within a volute 4141 such as the examplevolute illustrated in FIG. 5A so that the motor assembly may serve aspart of a blower of a flow generator.

8.2 Treatment Systems

In one form, the present technology comprises apparatus for treating arespiratory disorder. The apparatus may comprise a flow generator orblower including a switched reluctance motor for supplying pressurisedrespiratory gas, such as air, to the patient 1000 via an air deliverytube 4170 leading to a patient interface 3000.

8.3 Therapy

In one form, the present technology comprises method for treating arespiratory disorder comprising the step of applying positive pressureto the entrance of the airways of a patient 1000 using a pressure deviceincluding a switched reluctance motor.

8.3.1 Nasal CPAP for OSA

In one form, the present technology comprises a method of treatingObstructive Sleep Apnea in a patient by applying nasal continuouspositive airway pressure to the patient using a patient interface.

In certain embodiments of the present technology, a supply of air atpositive pressure is provided to the nasal passages of the patient viaone or both nares.

A patient interface 3000 is provided as seen in FIG. 4 to deliver thesupply of pressurized air to the patient's airways. A number ofdifferent types of patient interfaces including non-invasive andinvasive interfaces are available. For example non-invasive masksinclude a nasal mask, full face mask, nasal prongs and nasal pillows andinvasive interfaces include a tracheostomy tube. Non-invasive patientinterfaces 3000 comprise a seal-forming structure to engage with apatient's face in use.

8.4 Pap Device 4000

As shown in FIGS. 5A to 5D a PAP device 4000 in accordance with oneaspect of the present technology comprises mechanical and pneumaticcomponents 4100, electrical components 4200 and is programmed to executeone or more algorithms 4300. The PAP device preferably has an externalhousing 4010, preferably formed in two parts, an upper portion 4012 ofthe external housing 4010, and a lower portion 4014 of the externalhousing 4010. In alternative forms, the external housing 4010 mayinclude one or more panel(s) 4015. Preferably the PAP device 4000comprises a chassis 4016 that supports one or more internal componentsof the PAP device 4000. In one form a pneumatic block 4020 is supportedby, or formed as part of the chassis 4016. The PAP device 4000 mayoptionally include a handle 4018.

The pneumatic path of the PAP device 4000 preferably comprises an inletair filter 4112, an inlet muffler 4122, a controllable pressure device4140 capable of supplying air at positive pressure (preferably a blower4142) including a motor 4144, and an outlet muffler 4124. One or moretransducers 4270 such as pressure sensors 4274, flow sensors 4272 andspeed sensors 4276 are included in the pneumatic path.

The preferred pneumatic block 4020 comprises a portion of the pneumaticpath that is located within the external housing 4010.

The PAP device 4000 may include an electrical power supply 4210, one ormore input devices 4220, a central controller 4230, a therapy devicecontroller 4240, a therapy device 4245, one or more protection circuits4250, memory 4260, transducers 4270, data communication interface 4280and one or more output devices 4290. Electrical components 4200 may bemounted on a single Printed Circuit Board Assembly (PCBA) 4202. In analternative form, the PAP device 4000 may include more than one PCBA4202.

The central controller 4230 of the PAP device 4000 is programmed toexecute one or more algorithm modules 4300, preferably including apre-processing module 4310, a therapy engine module 4320, a therapycontrol module 4330, and further preferably a fault condition module4340.

8.4.1 PAP Device Mechanical & Pneumatic Components 4100

8.4.1.1 Air Filter(s) 4110

A PAP device in accordance with one form of the present technology mayinclude an air filter 4110, or a plurality of air filters 4110.

In one form, an inlet air filter 4112 is located at the beginning of thepneumatic path upstream of a blower 4142. See FIG. 5B.

In one form, an outlet air filter 4114, for example an antibacterialfilter, is located between an outlet of the pneumatic block 4020 and apatient interface 3000. See FIG. 5B.

8.4.1.2 Muffler(s) 4120

In one form of the present technology, an inlet muffler 4122 is locatedin the pneumatic path upstream of a blower 4142. See FIG. 5B.

In one form of the present technology, an outlet muffler 4124 is locatedin the pneumatic path between the blower 4142 and a patient interface3000. See FIG. 5B.

8.4.1.3 Pressure Device 4140

In a preferred form of the present technology, a pressure device 4140for producing a flow of air at positive pressure is a controllableblower 4142. For example the blower may include a switched reluctancemotor 4144 with one or more impellers housed in a volute. The blower maybe preferably capable of delivering a supply of air, for example about120 litres/minute, at a positive pressure in a range from about 4 cmH₂Oto about 20 cmH₂O, or in other forms up to about 30 cmH₂O.

The pressure device 4140 is under the control of the therapy devicecontroller 4240.

8.4.1.4 Transducer(s) 4270

In one form of the present technology, one or more transducers 4270 arelocated upstream of the pressure device 4140. The one or moretransducers 4270 are constructed and arranged to measure properties ofthe air at that point in the pneumatic path.

In one form of the present technology, one or more transducers 4270 arelocated downstream of the pressure device 4140, and upstream of the aircircuit 4170. The one or more transducers 4270 are constructed andarranged to measure properties of the air at that point in the pneumaticpath.

In one form of the present technology, one or more transducers 4270 arelocated proximate to the patient interface 3000.

8.4.1.5 Anti-Spill Back Valve 4160

In one form of the present technology, an anti-spill back valve islocated between the humidifier 5000 and the pneumatic block 4020. Theanti-spill back valve is constructed and arranged to reduce the riskthat water will flow upstream from the humidifier 5000, for example tothe motor 4144.

8.4.1.6 Air Circuit 4170

An air circuit 4170 in accordance with an aspect of the presenttechnology is constructed and arranged to allow a flow of air orbreathable gasses between the pneumatic block 4020 and the patientinterface 3000.

8.4.1.7 Oxygen Delivery 4180

In one form of the present technology, supplemental oxygen 4180 isdelivered to a point in the pneumatic path.

In one form of the present technology, supplemental oxygen 4180 isdelivered upstream of the pneumatic block 4020.

In one form of the present technology, supplemental oxygen 4180 isdelivered to the air circuit 4170.

In one form of the present technology, supplemental oxygen 4180 isdelivered to the patient interface 3000.

8.4.2 PAP Device Electrical Components 4200

8.4.2.1 Power Supply 4210

Power supply 4210 supplies power to the other components of the basicPAP device 4000: the input device 4220, the central controller 4230, thetherapy device 4245, and the output device 4290.

In one form of the present technology, power supply 4210 is internal ofthe external housing 4010 of the PAP device 4000. In another form of thepresent technology, power supply 4210 is external of the externalhousing 4010 of the PAP device 4000.

In one form of the present technology power supply 4210 provideselectrical power to the PAP device 4000 only. In another form of thepresent technology, power supply 4210 provides electrical power to bothPAP device 4000 and humidifier 5000.

8.4.2.2 Input Device(s) 4220

A PAP device 4000 may include one or more input devices 4220. Inputdevices 4220 comprises buttons, switches or dials to allow a person tointeract with the PAP device 4000. The buttons, switches or dials may bephysical devices, or software devices accessible via a touch screen. Thebuttons, switches or dials may, in one form, be physically connected tothe external housing 4010, or may, in another form, be in wirelesscommunication with a receiver that is in electrical connection to thecentral controller 4230.

In one form the input device 4220 may be constructed and arranged toallow a person to select a value and/or a menu option.

8.4.2.3 Central Controller or Processor 4230

In one form of the present technology, the central controller orprocessor 4230 is a dedicated electronic circuit configured to receiveinput signal(s) from the input device 4220, and to provide outputsignal(s) to the output device 4290 and/or the therapy device controller4240.

In one form, the central controller 4230 is an application-specificintegrated circuit. In another form, the central controller 4230comprises discrete electronic components.

In one form of the present technology, the central controller 4230 is aprocessor suitable to control a PAP device 4000 such as an x86 INTELprocessor.

A processor 4230 suitable to control a PAP device 4000 in accordancewith another form of the present technology includes a processor basedon ARM Cortex-M processor from ARM Holdings. For example, an STM32series microcontroller from ST MICROELECTRONICS may be used.

Another processor 4230 suitable to control a PAP device 4000 inaccordance with a further alternative form of the present technologyincludes a member selected from the family ARMS-based 32-bit RISC CPUs.For example, an STR9 series microcontroller from ST MICROELECTRONICS maybe used.

In certain alternative forms of the present technology, a 16-bit RISCCPU may be used as the processor 4230 for the PAP device 4000. Forexample a processor from the MSP430 family of microcontrollers,manufactured by TEXAS INSTRUMENTS, may be used.

The processor 4230 is configured to receive input signal(s) from one ormore transducers 4270, and one or more input devices 4220.

The processor 4230 is configured to provide output signal(s) to one ormore of an output device 4290, a therapy device controller 4240, a datacommunication interface 4280 and humidifier controller 5250.

In some forms of the present technology, the processor 4230, or multiplesuch processors, is configured to implement the one or moremethodologies described herein such as the one or more algorithms 4300expressed as computer programs stored in a non-transitory computerreadable storage medium, such as memory 4260. In some cases, aspreviously discussed, such processor(s) may be integrated with a PAPdevice 4000. However, in some forms of the present technology theprocessor(s) may be implemented discretely from the flow generationcomponents of the PAP device 4000, such as for purpose of performing anyof the methodologies described herein without directly controllingdelivery of a respiratory treatment. For example, such a processor mayperform any of the methodologies described herein for purposes ofdetermining control settings for a ventilator or other respiratoryrelated events by analysis of stored data such as from any of thesensors described herein.

Preferably PAP device 4000 includes a clock 4232 that is connected tothe central controller 4230.

8.4.2.4 Therapy Device 4245

In one form of the present technology, the therapy device 4245 isconfigured to deliver therapy to a patient 1000 under the control of thecentral controller 4230. Preferably the therapy device 4245 is apositive air pressure device 4140.

8.4.2.5 Therapy Device Controller 4240

In one form of the present technology, therapy device controller 4240 isa therapy control module 4330 such as for pressure control that formspart of the algorithms 4300 executed by the processor 4230.

In one form of the present technology, therapy device controller 4240 isa dedicated motor control integrated circuit. For example, in one form aMC33035 brushless DC motor controller, manufactured by ONSEMI is used.

8.4.2.6 Protection Circuits 4250

Preferably a PAP device 4000 in accordance with the present technologycomprises one or more protection circuits 4250.

One form of protection circuit 4250 in accordance with the presenttechnology is an electrical protection circuit.

One form of protection circuit 4250 in accordance with the presenttechnology is a temperature or pressure safety circuit.

8.4.2.7 Memory 4260

In accordance with one form of the present technology the PAP device4000 includes memory 4260, preferably non-volatile memory. In someforms, memory 4260 may include battery powered static RAM. In someforms, memory 4260 may include volatile RAM.

Preferably memory 4260 is located on PCBA 4202. Memory 4260 may be inthe form of EEPROM, or NAND flash.

Additionally or alternatively, PAP device 4000 includes removable formof memory 4260, for example a memory card made in accordance with theSecure Digital (SD) standard.

In one form of the present technology, the memory 4260 acts as anon-transitory computer readable storage medium on which is storedcomputer program instructions expressing the one or more methodologiesdescribed herein, such as the one or more algorithms 4300.

8.4.2.8 Transducers 4270

Transducers may be internal of the device, or external of the PAPdevice. External transducers may be located for example on or form partof the air delivery circuit, e.g. the patient interface. Externaltransducers may be in the form of non-contact sensors such as a Dopplerradar movement sensor that transmit or transfer data to the PAP device.

8.4.2.8.1 Flow

A flow transducer 4272 in accordance with the present technology may bebased on a differential pressure transducer, for example, an SDP600Series differential pressure transducer from SENSIRION. The differentialpressure transducer is in fluid communication with the pneumaticcircuit, with one of each of the pressure transducers connected torespective first and second points in a flow restricting element. Otherflow sensors may also be implemented such as a hot wire flow sensor.

In use, a signal representing total flow Qt from the flow transducer4272 is received by the processor 4230.

8.4.2.8.2 Pressure

A pressure transducer 4274 in accordance with the present technology islocated in fluid communication with the pneumatic circuit. An example ofa suitable pressure transducer is a sensor from the HONEYWELL ASDXseries. An alternative suitable pressure transducer is a sensor from theNPA Series from GENERAL ELECTRIC.

In use, a signal from the pressure transducer 4274, is received by theprocessor 4230. In one form, the signal from the pressure transducer4274 is filtered prior to being received by the processor 4230.

8.4.2.8.3 Motor Speed

In one form of the present technology a motor speed signal 4276 isgenerated. A motor speed signal 4276 is preferably provided by therapydevice controller 4240. Motor speed may, for example, be generated by aspeed sensor, such as a Hall effect sensor.

8.4.2.9 Data Communication Systems

In one preferred form of the present technology, a data communicationinterface 4280 is provided, and is connected to processor 4230. Datacommunication interface 4280 is preferably connectable to remoteexternal communication network 4282. Data communication interface 4280is preferably connectable to local external communication network 4284.Preferably remote external communication network 4282 is connectable toremote external device 4286. Preferably local external communicationnetwork 4284 is connectable to local external device 4288.

In one form, data communication interface 4280 is part of processor4230. In another form, data communication interface 4280 is anintegrated circuit that is separate from processor 4230.

In one form, remote external communication network 4282 is the Internet.The data communication interface 4280 may use wired communication (e.g.via Ethernet, or optical fibre) or a wireless protocol to connect to theInternet.

In one form, local external communication network 4284 utilises one ormore communication standards, such as Bluetooth, or a consumer infraredprotocol.

In one form, remote external device 4286 is one or more computers, forexample a cluster of networked computers. In one form, remote externaldevice 4286 may be virtual computers, rather than physical computers. Ineither case, such remote external device 4286 may be accessible to anappropriately authorised person such as a clinician.

Preferably local external device 4288 is a personal computer, mobilephone, tablet or remote control.

8.4.2.10 Output Devices Including Optional Display, Alarms

An output device 4290 in accordance with the present technology may takethe form of one or more of a visual, audio, and haptic output. A visualoutput may be a Liquid Crystal Display (LCD) or Light Emitting Diode(LED) display. An audio output may be a speaker or audio tone emitter.

8.4.2.10.1 Display Driver 4292

A display driver 4292 receives as an input the characters, symbols, orimages intended for display on the display 4294, and converts them tocommands that cause the display 4294 to display those characters,symbols, or images.

8.4.2.10.2 Display 4294

A display 4294 is configured to visually display characters, symbols, orimages in response to commands received from the display driver 4292.For example, the display 4294 may be an eight-segment display, in whichcase the display driver 4292 converts each character or symbol, such asthe figure “0”, to eight logical signals indicating whether the eightrespective segments are to be activated to display a particularcharacter or symbol.

8.4.3 PAP Device Algorithms 4300

8.4.3.1 Pre-Processing Module 4310

An pre-processing module 4310 in accordance with the present technologyreceives as an input, raw data from a transducer, for example a flow orpressure transducer, and preferably performs one or more process stepsto calculate one or more output values that will be used as an input toanother module, for example a therapy engine module 4320.

In one form of the present technology, the output values include theinterface or mask pressure Pm, the respiratory flow Qr, and the leakflow Ql.

In various forms of the present technology, the pre-processing module4310 comprises one or more of the following algorithms: pressurecompensation algorithm 4312, vent flow calculation algorithm 4314, leakflow algorithm 4316 and respiratory flow algorithm 4318.

A pressure compensation algorithm 4312 may receive as an input a signalindicative of the pressure in the pneumatic path proximal to an outletof the pneumatic block. The pressure compensation algorithm 4312estimates the pressure drop in the air circuit 4170 and provides as anoutput an estimated pressure, Pm, in the patient interface 3000.

A vent flow calculation algorithm 4314 may receive as an input anestimated pressure, Pm, in the patient interface 3000 and estimates avent flow of air, Qv, from a vent 3400 in a patient interface 3000.

A leak flow algorithm 4316 may receive as an input a total flow, Qt, anda vent flow Qv, and provides as an output a leak flow Ql by calculatingan average of Qt-Qv over a period sufficiently long to include severalbreathing cycles, e.g. about 10 seconds.

A respiratory flow algorithm 4318 may receive as an input a total flow,Qt, a vent flow, Qv, and a leak flow, Ql, and estimates a respiratoryflow of air, Qr, to the patient, by subtracting the vent flow Qv and theleak flow Ql from the total flow Qt.

8.4.3.2 Therapy Engine Module 4320

In one form of the present technology, a therapy engine module 4320 mayreceive as inputs one or more of a pressure, Pm, in a patient interface3000, and a respiratory flow of air to a patient, Qr, and provides as anoutput, one or more therapy parameters, such as a CPAP treatmentpressure Pt, a level of pressure support, and a target ventilation.

In various forms of the present technology, the therapy engine module4320 comprises one or more of the following algorithms: phasedetermination 4321, waveform determination 4322, ventilationdetermination 4323, flow limitation determination 4324, Apnea/hypopneadetermination 4325, Snore determination 4326, Patency determination 4327and Therapy parameter determination 4328.

A phase determination algorithm 4321 may receive as an input a signalindicative of respiratory flow, Qr, and provides as an output a phase ofa breathing cycle of a patient 1000. The phase output may be a discretevariable with values of one of inhalation, mid-inspiratory pause, andexhalation. Alternatively the phase output is a continuous variable, forexample varying from 0 to 1, or 0 to 2Pi.

In one form, the phase output is determined to have a discrete value ofinhalation when a respiratory flow Qr has a positive value that exceedsa positive threshold. In one form, a phase is determined to have adiscrete value of exhalation when a respiratory flow Qr has a negativevalue that is more negative than a negative threshold.

A waveform determination algorithm 4322 may receive as an input a valueindicative of current patient ventilation, Vent, and provides as anoutput a waveform of pressure vs. phase. A ventilation determinationalgorithm 4323 may receive as an input a respiratory flow Qr, anddetermines a measure indicative of patient ventilation, Vent. Forexample the ventilation determination algorithm 4323 may determine acurrent value of patient ventilation, Vent, as half the low-passfiltered absolute value of respiratory flow, Qr.

A flow limitation determination algorithm 4324 may receive as an input arespiratory flow signal Qr and provides as an output a metric of theextent to which the inspiratory portion of the breath exhibitsinspiratory flow limitation.

An Apnea/hypopnea determination algorithm 4325 may receive as an input arespiratory flow signal Qr and provide as an output a flag thatindicates that an apnea or an hypopnea has been detected.

An apnea may be said to have been detected when a function ofrespiratory flow Qr falls below a flow threshold for a predeterminedperiod of time. The function may determine a peak flow, a relativelyshort-term mean flow, or a flow intermediate of relatively short-termmean and peak flow, for example an RMS flow. The flow threshold may be arelatively long-term measure of flow.

A hypopnea may be said to have been detected when a function ofrespiratory flow Qr falls below a second flow threshold for apredetermined period of time. The function may determine a peak flow, arelatively short-term mean flow, or a flow intermediate of relativelyshort-term mean and peak flow, for example an RMS flow. The second flowthreshold may be a relatively long-term measure of flow. The second flowthreshold is greater than the flow threshold used to detect apneas.

A snore determination algorithm 4326 may receive as an input arespiratory flow signal Qr and provides as an output a metric of theextent to which snoring is present. Preferably the snore determinationalgorithm 4326 comprises the step of determining the intensity of theflow signal in the range of 30-300 Hz. Further preferably, snoredetermination algorithm 4326 comprises a step of filtering therespiratory flow signal Qr to reduce background noise, e.g. the sound ofairflow in the system from the blower. The snore determination algorithm4326 may comprise comparing the noise generated during inspiration tothe noise generated during expiration to determine the occurrence ofsnore, where the noise generated during expiration is considered torelate to the intrinsic device noise.

In one form an airway patency algorithm 4327 may receive as an input arespiratory flow signal Qr, and determines the power of the signal inthe frequency range of about 0.75 Hz and about 3 Hz. The presence of apeak in this frequency range is taken to indicate an open airway. Theabsence of a peak is taken to be an indication of a closed airway.

In one form, the frequency range within which the peak is sought is thefrequency of a small forced oscillation in the treatment pressure Pt. Inone implementation, the forced oscillation is of frequency 2 Hz withamplitude about 1 cmH₂0.

In another form, an airway patency algorithm 4327 may receive as aninput a respiratory flow signal Qr, and determines the presence orabsence of a cardiogenic signal. The absence of a cardiogenic signal istaken to be an indication of a closed airway.

A therapy parameter determination algorithm 4328 determines a targettreatment pressure Pt to be delivered by the PAP device 4000. Thetherapy parameter determination algorithm 4328 receives as an input oneof more of the following:

i. A measure of respiratory phase;

ii. A waveform;

iii. A measure of ventilation;

iv. A measure of inspiratory flow limitation;

v. A measure of the presence of apnea and/or hypopnea;

vi. A measure of the presence of snore; and

vii. A measure of the patency of the airway.

The therapy parameter determination algorithm 4328 determines thetreatment pressure Pt as a function of indices or measures of one ormore of flow limitation, apnea, hypopnea, patency, and snore. In oneimplementation, these measures are determined on a single breath basis,rather than on an aggregation of several previous breaths.

FIG. 5E is a flow chart illustrating a method 4500 carried out by theprocessor 4230 as one implementation of the algorithm 4328. The method4500 starts at step 4520, at which the processor 4230 compares themeasure of the presence of apnea/hypopnea with a first threshold, anddetermines whether the measure of the presence of apnea/hypopnea hasexceeded the first threshold for a predetermined period of time,indicating an apnea/hypopnea is occurring. If so, the method 4500proceeds to step 4540; otherwise, the method 4500 proceeds to step 4530.At step 4540, the processor 4230 compares the measure of airway patencywith a second threshold. If the measure of airway patency exceeds thesecond threshold, indicating the airway is patent, the detectedapnea/hypopnea is deemed central, and the method 4500 proceeds to step4560; otherwise, the apnea/hypopnea is deemed obstructive, and themethod 4500 proceeds to step 4550.

At step 4530, the processor 4230 compares the measure of flow limitationwith a third threshold. If the measure of flow limitation exceeds thethird threshold, indicating inspiratory flow is limited, the method 4500proceeds to step 4550; otherwise, the method 4500 proceeds to step 4560.

At step 4550, the processor 4230 increases the treatment pressure Pt bya predetermined pressure increment ΔP, provided the increased treatmentpressure Pt would not exceed an upper limit Pmax. In one implementation,the predetermined pressure increment ΔP and upper limit Pmax are 1 cmH₂0and 20 cmH₂0 respectively. The method 4500 then returns to step 4520.

At step 4560, the processor 4230 decreases the treatment pressure Pt bya decrement, provided the decreased treatment pressure Pt would not fallbelow a lower limit Pmin, such as a Pmin of 4 cmH₂0. The method 4500then returns to step 4520. In one implementation, the decrement isproportional to the value of Pt-Pmin, so that the decrease in Pt to thelower limit Pmin in the absence of any detected events is exponential.Alternatively, the decrement in Pt could be predetermined, so thedecrease in Pt to the lower limit Pmin in the absence of any detectedevents is linear.

8.4.3.3 Therapy Control Module 4330

A therapy control module 4330 in accordance with one aspect of thepresent technology may receive as an input a target treatment pressurePt, and controls a therapy device 4245 to deliver that pressure. Thetherapy control module 4330 may receive as an input an EPAP pressure andan IPAP pressure, and controls a therapy device 4245 to deliver thoserespective pressures.

8.4.3.4 Detection of Fault Conditions

In one form of the present technology, a processor executes one or moremethods for the detection of fault conditions serving as a faultcondition module 4340. Preferably the fault conditions detected by theone or more methods includes at least one of the following:

-   -   Power failure (no power, or insufficient power)    -   Transducer fault detection    -   Failure to detect the presence of a component    -   Operating parameters outside recommended ranges (e.g. pressure,        flow, temperature, PaO₂)    -   Failure of a test alarm to generate a detectable alarm signal.

Upon detection of the fault condition, the corresponding algorithmsignals the presence of the fault by one or more of the following:

-   -   Initiation of an audible, visual &/or kinetic (e.g. vibrating)        alarm    -   Sending a message to an external device    -   Logging of the incident        8.5 Humidifier 5000        8.5.1 Humidifier Overview

As shown in FIGS. 6A and 6B, a humidifier 5000 comprising a waterreservoir 5110 and a heating plate 5120 may be provided and configuredto couple directly or indirectly with a PAP device 4000. The waterreservoir 5110 is configured to hold a supply of water 5300 that isheated by the heater plate 5120. The water reservoir 5110 may hold agiven, maximum volume of liquid (e.g. water), typically several hundredmillilitres. The water reservoir 5110 is arranged to receive a flow ofbreathable gas from the PAP device 4000 through an air inlet and to addhumidity to the breathable gas. The humidified breathable gas exits thehumidifier via an outlet for delivery to a patient interface (not shown)via an air delivery conduit 4170. The air delivery conduit may include aheated air delivery conduit 4172.

One or more transducers or sensors 5270, such as a temperature sensor, arelative humidity sensor, an absolute humidity sensor, a flow sensor orother such sensors may be present at one or more locations along the airpath to measure the temperature, relative humidity, absolute humidity orflow rate at different locations to assist in controlling the humidifierand an optional heated air delivery conduit 4172. For example the heaterplate 5120 may comprise a temperature sensor to measure the temperatureof the heating plate. The one or more transducers or sensors 5270 mayalso be located external to the air path to measure the ambientconditions such as ambient temperature, ambient relative humidity and/orambient absolute humidity.

A heated air delivery conduit 4172 may comprise a heating element 4173within or around the heated air delivery conduit 4172. For example wiresmay be positioned between the film and supporting ribs of a heated tube.The heated air delivery conduit 4172 may also comprise one or moretransducers or sensors 5270 as described above.

8.6 Glossary

For the purposes of the present technology disclosure, in certain formsof the present technology, one or more of the following definitions mayapply. In other forms of the present technology, alternative definitionsmay apply.

Air: In certain forms of the present technology, air supplied to apatient may be atmospheric air, and in other forms of the presenttechnology atmospheric air may be supplemented with oxygen.

Continuous Positive Airway Pressure (CPAP): CPAP treatment will be takento mean the application of a supply of air or breathable gas to theentrance to the airways at a pressure that is continuously positive withrespect to atmosphere, and preferably approximately constant through arespiratory cycle of a patient. In some forms, the pressure at theentrance to the airways will vary by a few centimeters of water within asingle respiratory cycle, for example being higher during inhalation andlower during exhalation. In some forms, the pressure at the entrance tothe airways will be slightly higher during exhalation, and slightlylower during inhalation. In some forms, the pressure will vary betweendifferent respiratory cycles of the patient, for example being increasedin response to detection of indications of partial upper airwayobstruction, and decreased in the absence of indications of partialupper airway obstruction.

Controller: A device, or portion of a device that adjusts an outputbased on an input. For example one form of controller has a variablethat is under control—the control variable—that constitutes the input tothe device. The output of the device is a function of the current valueof the control variable, and a set point for the variable. Aservo-ventilator may include a controller that has ventilation as aninput, a target ventilation as the set point, and level of pressuresupport as an output. Other forms of input may be one or more of oxygensaturation (SaO₂), partial pressure of carbon dioxide (PCO₂), movement,a signal from a photoplethysmogram, and peak flow. The set point of thecontroller may be one or more of fixed, variable or learned. Forexample, the set point in a ventilator may be a long term average of themeasured ventilation of a patient. Another ventilator may have aventilation set point that changes with time. A pressure controller maybe configured to control a blower or pump to deliver air at a particularpressure.

Therapy: Therapy in the present context may be one or more of positivepressure therapy, oxygen therapy, carbon dioxide therapy, control ofdead space, and the administration of a drug.

Transducers: A device for converting one form of energy or signal intoanother. A transducer may be a sensor or detector for convertingmechanical energy (such as movement) into an electrical signal. Examplesof transducers include pressure sensors, flow sensors, carbon dioxide(CO₂) sensors, oxygen (O₂) sensors, effort sensors, movement sensors,noise sensors, a plethysmograph, and cameras.

Volute: The casing of the centrifugal pump that receives the air beingpumped by the impeller, slowing down the flow rate of air and increasingthe pressure. The cross-section of the volute increases in area towardsthe discharge port.

Apnea: Preferably, apnea will be said to have occurred when flow fallsbelow a predetermined threshold for a duration, e.g. 10 seconds. Anobstructive apnea will be said to have occurred when, despite patienteffort, some obstruction of the airway does not allow air to flow. Acentral apnea will be said to have occurred when an apnea is detectedthat is due to a reduction in breathing effort, or the absence ofbreathing effort.

Breathing rate: The rate of spontaneous respiration of a patient,usually measured in breaths per minute.

Effort (breathing): Preferably breathing effort will be said to be thework done by a spontaneously breathing person attempting to breathe.

Expiratory portion of a breathing cycle: The period from the start ofexpiratory flow to the start of inspiratory flow.

Flow limitation: Preferably, flow limitation will be taken to be thestate of affairs in a patient's respiration where an increase in effortby the patient does not give rise to a corresponding increase in flow.Where flow limitation occurs during an inspiratory portion of thebreathing cycle it may be described as inspiratory flow limitation.Where flow limitation occurs during an expiratory portion of thebreathing cycle it may be described as expiratory flow limitation.

Hypopnea: Preferably, a hypopnea will be taken to be a reduction inflow, but not a cessation of flow. In one form, a hypopnea may be saidto have occurred when there is a reduction in flow below a threshold fora duration. In one form in adults, the following either of the followingmay be regarded as being hypopneas:

-   -   (i) a 30% reduction in patient breathing for at least 10 seconds        plus an associated 4% desaturation; or    -   (ii) a reduction in patient breathing (but less than 50%) for at        least 10 seconds, with an associated desaturation of at least 3%        or an arousal.

Patency (airway): The degree of the airway being open, or the extent towhich the airway is open. A patent airway is open. Airway patency may bequantified, for example with a value of one (1) being patent, and avalue of zero (0), being closed.

Positive End-Expiratory Pressure (PEEP): The pressure above atmospherein the lungs that exists at the end of expiration.

Peak flow (Qpeak): The maximum value of flow during the inspiratoryportion of the respiratory flow waveform.

Respiratory flow, airflow, patient airflow, respiratory airflow (Qr):These synonymous terms may be understood to refer to the PAP device'sestimate of respiratory airflow, as opposed to “true respiratory flow”or “true respiratory airflow”, which is the actual respiratory flowexperienced by the patient, usually expressed in litres per minute.

Upper airway obstruction (UAO): includes both partial and total upperairway obstruction. This may be associated with a state of flowlimitation, in which the level of flow increases only slightly or mayeven decrease as the pressure difference across the upper airwayincreases (Starling resistor behaviour).

Ventilation (Vent): A measure of the total amount of gas being exchangedby the patient's respiratory system, including both inspiratory andexpiratory flow, per unit time. When expressed as a volume per minute,this quantity is often referred to as “minute ventilation”. Minuteventilation is sometimes given simply as a volume, understood to be thevolume per minute.

Flow rate: The instantaneous volume (or mass) of air delivered per unittime. While flow rate and ventilation have the same dimensions of volumeor mass per unit time, flow rate is measured over a much shorter periodof time. Flow may be nominally positive for the inspiratory portion of abreathing cycle of a patient, and hence negative for the expiratoryportion of the breathing cycle of a patient. In some cases, a referenceto flow rate will be a reference to a scalar quantity, namely a quantityhaving magnitude only. In other cases, a reference to flow rate will bea reference to a vector quantity, namely a quantity having bothmagnitude and direction. Flow will be given the symbol Q. Total flow,Qt, is the flow of air leaving the PAP device. Vent flow, Qv, is theflow of air leaving a vent to allow washout of exhaled gases. Leak flow,Ql, is the flow rate of unintentional leak from a patient interfacesystem. Respiratory flow, Qr, is the flow of air that is received intothe patient's respiratory system.

Leak: Preferably, the word leak will be taken to be a flow of air to theambient. Leak may be intentional, for example to allow for the washoutof exhaled CO₂. Leak may be unintentional, for example, as the result ofan incomplete seal between a mask and a patient's face.

Pressure: Force per unit area. Pressure may be measured in a range ofunits, including cmH₂O, g-f/cm², hectopascal. 1cmH₂O is equal to 1g-f/cm² and is approximately 0.98 hectopascal. In this specification,unless otherwise stated, pressure is given in units of cmH₂O. For nasalCPAP treatment of OSA, a reference to treatment pressure is a referenceto a pressure in the range of about 4-20 cmH₂O, or about 4-30 cmH₂O. Thepressure in the patient interface is given the symbol Pm.

Sound Power: The energy per unit time carried by a sound wave. The soundpower is proportional to the square of sound pressure multiplied by thearea of the wavefront. Sound power is usually given in decibels SWL,that is, decibels relative to a reference power, normally taken as 10⁻¹²watt.

Sound Pressure: The local deviation from ambient pressure at a giventime instant as a result of a sound wave travelling through a medium.Sound power is usually given in decibels SPL, that is, decibels relativeto a reference power, normally taken as 20×10⁻⁶ pascal (Pa), consideredthe threshold of human hearing.

8.7 Other Remarks

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

Unless the context clearly dictates otherwise and where a range ofvalues is provided, it is understood that each intervening value, to thetenth of the unit of the lower limit, between the upper and lower limitof that range, and any other stated or intervening value in that statedrange is encompassed within the technology. The upper and lower limitsof these intervening ranges, which may be independently included in theintervening ranges, are also encompassed within the technology, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the technology.

Furthermore, where a value or values are stated herein as beingimplemented as part of the technology, it is understood that such valuesmay be approximated, unless otherwise stated, and such values may beutilized to any suitable significant digit to the extent that apractical technical implementation may permit or require it.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this technology belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present technology, a limitednumber of the exemplary methods and materials are described herein.

When a particular material is identified as being preferably used toconstruct a component, obvious alternative materials with similarproperties may be used as a substitute. Furthermore, unless specified tothe contrary, any and all components herein described are understood tobe capable of being manufactured and, as such, may be manufacturedtogether or separately.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include their plural equivalents,unless the context clearly dictates otherwise.

All publications mentioned herein are incorporated by reference todisclose and describe the methods and/or materials which are the subjectof those publications. The publications discussed herein are providedsolely for their disclosure prior to the filing date of the presentapplication. Nothing herein is to be construed as an admission that thepresent technology is not entitled to antedate such publication byvirtue of prior invention. Further, the dates of publication providedmay be different from the actual publication dates, which may need to beindependently confirmed.

Moreover, in interpreting the disclosure, all terms should beinterpreted in the broadest reasonable manner consistent with thecontext. In particular, the terms “comprises” and “comprising” should beinterpreted as referring to elements, components, or steps in anon-exclusive manner, indicating that the referenced elements,components, or steps may be present, or utilized, or combined with otherelements, components, or steps that are not expressly referenced.

The subject headings used in the detailed description are included onlyfor the ease of reference of the reader and should not be used to limitthe subject matter found throughout the disclosure or the claims. Thesubject headings should not be used in construing the scope of theclaims or the claim limitations.

Although the technology herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thetechnology. In some instances, the terminology and symbols may implyspecific details that are not required to practice the technology. Forexample, although the terms “first” and “second” may be used, unlessotherwise specified, they are not intended to indicate any order but maybe utilised to distinguish between distinct elements. Furthermore,although process steps in the methodologies may be described orillustrated in an order, such an ordering is not required. Those skilledin the art will recognize that such ordering may be modified and/oraspects thereof may be conducted concurrently or even synchronously.

Further example versions of the technology may be considered in thefollowing descriptive paragraphs:

Example 1

A poly-phase switched reluctance motor assembly comprising:

a stator assembly including a plurality of coils and a stator with acentral bore, and

a rotor assembly having a plurality of poles, the rotor assembly beingarranged within the central bore of the stator assembly and configuredto rotate therein,

wherein the plurality of coils are configured in a distributed windingconfiguration,

wherein the stator includes a plurality of projecting stator teethforming a plurality of stator slots therebetween, and

wherein a total number of stator slots is a multiple of number of phasesand number of rotor poles of the motor.

Example 2

The poly-phase switched reluctance motor assembly of Example 1 whereineach of the plurality of stator slots comprises a coil segment from oneof the plurality of coils.

Example 3

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-2, wherein the total number of stator slots furthercomprises a multiple of a winding distribution parameter, such that thetotal number of stator slots satisfies an equation consisting of:Total number of stator slots=number of phases×number of rotorpoles×winding distribution parameter.

Example 4

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-3, wherein the plurality of coils includes a coil groupfor each phase of the poly-phase switched reluctance motor and each ofthe coils in a coil group includes a pair of coil segments, the coilsegments for each coil group are uniformly distributed between thestator slots.

Example 5

The poly-phase switched reluctance motor assembly according to Example4, wherein each coil group comprises at least one coil.

Example 6

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-5, including at least three motor phases and wherein inuse two motor phases are energized and at least one phase isnon-energized during a conduction period.

Example 7

The poly-phase switched reluctance motor assembly according to Example6, wherein one of the two energized phases is switched off to anon-energized state and one of the non-energized phases is switched onto an energized state during each commutation period.

Example 8

The poly-phase switched reluctance motor assembly according to any oneof Examples 6 or 7, wherein one of the two energized phases is providedwith a positive direction current and the other of the two energizedphases is provided with a negative direction current.

Example 9

The poly-phase switched reluctance motor assembly according to Example8, wherein each phase of the motor is energized with a current valueduring at least two consecutive conduction periods.

Example 10

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-9, having an inductance ratio of less than 3.

Example 11

The poly-phase switched reluctance motor assembly according to Example10, wherein the inductance ratio is between 2 and 2.5.

Example 12

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-11, wherein the stator has an outer diameter less than 50mm.

Example 13

The poly-phase switched reluctance motor assembly according to Example12, wherein the stator has an outer diameter less than or equal to 45mm.

Example 14

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-13, wherein width of each rotor pole is wider than widthof one of the plurality of stator teeth.

Example 15

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-14, wherein the distributed winding configurationcomprises a plurality of phases with at least one phase of the pluralityof phases comprising a plurality of coil winding groups.

Example 16

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-15 wherein each rotor pole width is equal.

Example 17

The poly-phase switched reluctance motor assembly according to any oneof Examples 1-16 wherein each stator slot width is equal.

Example 18

The poly-phase switched reluctance motor assembly of any one of Examples1-17 wherein the stator assembly and rotor assembly are configured tohave a difference between a stator central angle and a rotor centralangle in a difference range of 5 to 30 degrees.

Example 19

The poly-phase switched reluctance motor assembly of Example 18 whereinthe difference between a stator central angle and a rotor central angleis about 27 degrees.

Example 20

The poly-phase switched reluctance motor assembly of any one of Examples1-19 wherein each of the stator teeth comprises teeth tips.

Example 21

A stator assembly for a poly-phase switched reluctance motor comprising

a plurality of stator teeth separated by stator slots and surrounding acentral bore,

a plurality of coils that are configured in a distributed windingconfiguration, the plurality of coils includes a coil group for eachphase of the poly-phased switched reluctance motor,

wherein the central bore is configured to receive a rotor assemblyhaving a plurality of poles and a total number of stator slots is amultiple of number of phases and number of rotor poles of the motor.

Example 22

The stator assembly according to Example 21, wherein each of the statorslots comprises a coil segment of one of the coils of the plurality ofcoils.

Example 23

The stator assembly according to any one of Examples 21-22, wherein eachcoil group comprises at least one coil.

Example 24

The stator assembly according to any one of Examples 21-23, wherein awidth of each of the stator teeth of the plurality of stator teeth isless than a width of a rotor pole.

Example 25

The stator assembly according to any one of Examples 21-24, wherein thedistributed winding configuration comprises a plurality of phases withat least one phase of the plurality of phases comprising a plurality ofcoil winding groups.

Example 26

The stator assembly according to any one of Examples 21-25 wherein rotorpoles of the received rotor assembly have widths that are equal.

Example 27

The stator assembly according to any one of Examples 21-26 wherein eachstator tooth width is equal.

Example 28

The stator assembly according to any one of Examples 21-27, wherein thetotal number of stator slots comprises a further multiple of a windingdistribution parameter such that the total number of stator slotssatisfies an equation consisting of:Total number of stator slots=number of phases×number of rotorpoles×winding distribution parameter.

Example 29

The stator assembly according to any one of Examples 21-28, wherein eachof the coil segments for a coil group are uniformly distributed betweenthe stator slots.

Example 30

The stator assembly according to any one of Examples 21-29, having aninductance ratio of less than 3.

Example 31

The stator assembly according to Example 30, wherein the inductanceratio is between 2 and 2.5.

Example 32

The stator assembly according to any one of Examples 21-31, wherein thestator has an outer diameter less than 50 mm.

Example 33

The stator assembly according to Example 32, wherein the stator has anouter diameter less than or equal to 45 mm.

Example 34

The stator assembly of any one of Examples 21-33 wherein the statorassembly and rotor assembly are configured to have a difference betweena stator central angle and a rotor central angle in a difference rangeof 5 to 30 degrees.

Example 35

The stator assembly of Example 34 wherein the difference between thestator central angle and the rotor central angle is about 27 degrees.

Example 36

The stator assembly of any one of Examples 21-35 wherein each of thestator teeth comprises teeth tips.

Example 37

A positive airway pressure device comprising a poly-phase switchedreluctance motor according to any one of Examples 1-20 configured toprovide a supply of pressurized breathable gas.

Example 38

A system for treating a respiratory disorder comprising:

a therapy device comprising a poly-phase switched reluctance motoraccording to any one of Examples 1-20 configured to provide a supply ofpressurized breathable gas;

an air delivery conduit; and

a patient interface configured to receive the supply of pressurized gasfrom the therapy device via the air delivery conduit and deliver thesupply of pressurized gas to a patient.

Example 39

The system according to Example 38 further comprising a humidifierconfigured to humidify the supply of pressurized gas.

Example 40

A method of controlling a switched reluctance motor, the switchedreluctance motor comprising at least three phases, the methodcomprising:

during each conduction period energizing a first phase with a negativedirection current, energizing a second phase with a positive current andhaving at least one non-energized phase; and

during each commutation period switching off one of the first phase orthe second phase to a non-energized state and switching on one of thenon-energized phases to an energized state with a same direction currentas the first or second phase that was switched off.

Example 41

The method according to Example 40, wherein the switched reluctancemotor includes a distributed winding configuration.

Example 42

The method of any one of Examples 40-41 wherein the switched reluctancemotor has a total number of stator slots that is a multiple of number ofphases and number of rotor poles.

Example 43

The method of Example 42 wherein the total number of stator slotsfurther comprises a multiple of a winding distribution parameter.

Example 44

The method of any one of Examples 40-43 wherein the switched reluctancemotor has a stator assembly and rotor assembly configured to have adifference between a stator central angle and a rotor central angle in adifference range of 5 to 30 degrees.

Example 45

The method of Example 44 wherein the difference between the statorcentral angle and the rotor central angle is about 27 degrees.

Example 46

The method of any one of Examples 40-45 wherein the switched reluctancemotor has a plurality of stator teeth, each comprising teeth tips.

Example 47

The method of any one of Examples 40-46 wherein the switched reluctancemotor has only three phases.

Example 48

The method of any one of Examples 40-47 wherein the switched reluctancemotor is a component of a therapy device configured to supplypressurized gas.

It is therefore to be understood that numerous modifications may be madeto the illustrative embodiments and that other arrangements may bedevised without departing from the spirit and scope of the technology.

The invention claimed is:
 1. A stator assembly for a poly-phase switchedreluctance motor comprising: a plurality of stator teeth separated bystator slots and surrounding a central bore; and a plurality of coilsthat are configured in a distributed winding configuration, theplurality of coils including a coil group for each phase of thepoly-phased switched reluctance motor, wherein the central bore isconfigured to receive a rotor assembly including a rotor having aplurality of rotor poles and a total number of stator slots is amultiple of number of phases and number of rotor poles of the poly-phaseswitched reluctance motor, wherein a sum of a width of each stator toothof the plurality of stator teeth and each width of gaps adjacent to thestator tooth is equal to a width of each rotor pole of the plurality ofrotor poles, wherein the stator assembly includes at least three phases;and wherein, when the stator assembly is configured with the rotorassembly for use in the polyphase switched reluctance motor to operatewith at least three phases that have direct current applied, at least inpart, as a positive direction current and a negative direction current.2. The stator assembly according to claim 1, wherein each of the statorslots comprises a coil segment of one of the coils of the plurality ofcoils.
 3. The stator assembly according to claim 2, wherein each of thecoil segments for a coil group are uniformly distributed between thestator slots.
 4. The stator assembly according to claim 1, wherein eachcoil group comprises at least one coil.
 5. The stator assembly accordingto claim 1, wherein the width of each of the stator teeth of theplurality of stator teeth is less than the width of the rotor pole. 6.The stator assembly according to claim 1, wherein the distributedwinding configuration comprises a plurality of phases with at least onephase of the plurality of phases comprising a plurality of coil windinggroups.
 7. The stator assembly according to claim 1, wherein the rotorpoles of the received rotor assembly have widths that are equal.
 8. Thestator assembly according to claim 1, wherein each stator tooth width isequal.
 9. The stator assembly according to claim 1, wherein the totalnumber of stator slots comprises a further multiple of a windingdistribution parameter such that the total number of stator slotssatisfies an equation consisting of:Total number of stator slots=number of phases×number of rotorpoles×winding distribution parameter.
 10. The stator assembly accordingto claim 1, wherein the poly-phase switched reluctance motor has aninductance ratio of less than
 3. 11. The stator assembly according toclaim 10, wherein the inductance ratio is between 2 and 2.5.
 12. Thestator assembly according to claim 1, wherein the stator has an outerdiameter less than 50 mm.
 13. The stator assembly according to claim 12,wherein the stator has an outer diameter less than or equal to 45 mm.14. The stator assembly of claim 1, wherein the stator assembly androtor assembly are configured to have a difference between a statorcentral angle and a rotor central angle in a difference range of 5degrees to 30 degrees.
 15. The stator assembly of claim 14, wherein thedifference between the stator central angle and the rotor central angleis about 27 degrees.
 16. The stator assembly of claim 1, wherein each ofthe stator teeth comprises teeth tips.
 17. The stator assembly of claim1, wherein the poly-phase switched reluctance motor is configured withan impeller.
 18. The stator assembly of claim 17, wherein the poly-phaseswitched reluctance motor with the impeller is configured to produce aflow of air.
 19. The stator assembly of claim 17, wherein the poly-phaseswitched reluctance motor with the impeller is configured within avolute of a blower.
 20. The stator assembly according to claim 1,wherein the width of each of the gaps is a width of the stator slot atan inner end of the stator slot, the inner end being an end closest tothe rotor.
 21. The stator assembly according to claim 1, wherein thestator assembly is configured for at least three phases, and wherein twophases of the at least three phases are energized with a positivedirection current and a negative direction current, and at least onephase is non-energized.